Is it ok to run 85 octane unleaded in my 5.4L?, it recommends using 87 is there a big difference?

It seems to run ok and in Colorado my choices are 85,87,91 octane, price is reason for running lower octane.


Thanks

 

Was it a stupid question?, 40 views not 1 reply.

 

I would suggest staying with 87. Lower octane rating often give much lower mpg due to the detuning by the cpu for no damage running. My PT cruiser GT will run on 87 but drinks it compared to 93 thus killing the price diff.

 

In my opinion you'd be risking your engine. Knocking really beats-up an engine. Whatever you saved buying the cheaper gas you'd lose in lower gas milage. The Knock Sensors signaling to back-off the timing all the time will destroy your MPG.

 

Hi Padron,

Your engine was designed to use 87 octane from the factory - now you *might* be able to get away with 85 octane, as the knock sensor might catch it well enough and keep you out of detonation - but you'll lose power and performance, as well as fuel economy.

These trucks generally *do* allow for operation on 85 octane in areas where 85 octane is actually "regular" grade fuel - such as in very high altitudes (which you will have in some areas of Colorado, for example), or down in Mexico - some of them will detonate on 85, and some won't.

Personally, I would never do it, but you can always give it a try with a small amount - in other words, run the tank down low, and only put in about 1/4 to 1/3 tank of 85, drive it around a bit, and see how it responds - if you don't have any problems with detonation (spark knock, pinging), then you might be OK. And if you do, then you can add enough higher octane fuel to it to level it out, and then just use 87 from then on. That's really the only way to tell for sure.

Good luck!

 

Thanks for the help

 

You're very welcome - One last point - whatever fuel you use, stick to major name brands, steering clear of what we refer to as off-brand or "no-name" fuels - that way you'll generally get a higher energy content & better detergent additives, which will help your MPG, performance, and help keep the fuel delivery system and top end of the motor cleaner.

 

You're in Denver, at that altitude 85 is fine and will perform the same as 87 at a lower altitude. You need less octane due to the lower oxygen levels in the air up there.

I just noticed this is the chips and performance forum...If you have a chip or other mods on the truck run the 91, I was assuming a stock motor.

 

Hey guys. First time to post here but love the site. This thread got me thinking a little. I am in Denver too and am about to order chip tuner, cold air intake, performance exhaust, and underdrive pulleys for the 5.4L. I've been running 85 oct for the last couple of years on the stock motor. Planned on 87 oct after the mods. Should I reconsider and run 91 only?

Thanks in advance for any advice.

 

Hi Pintail,

When you order the XCalibrator 2 from us to get our custom tuning, we'll provide a set of 3 different custom tunes - so you'll have plenty of room for an 87 octane tune as well as tuning for 91 octane, too.

We generally advise having at least one of those 3 tunes be made for 87 octane ("regular" gas), so that you can run lower octane if you want or need to and still have better performance and driveability than you did on the stock factory tune. Then we can set up your other tunes however you like, for 91 octane, towing tunes, pure performance tunes, etc., whatever works best for your individual needs.

Now it is true that a lot of us always run our premium gas performance tunes, simply because that is what gets the highest possible power & performance gains, and usually the best MPG, too - but the idea is to have maximum flexibility, and that's what our 3 different programs in the XCalibrator 2 will give you, so you've got room for 87 octane tuning as well as 91 octane tuning - or 89 octane, 93 octane, etc., whatever is appropriate for where you live.

When you call in to place your order with us, we go over all of that in detail, and help you select the best combination of 3 different tunes that will best suit your needs - that's all part of our normal procedure, so we'll go over all of that with you in detail at that time as well.

If you'd like to go over any of this in more detail, feel free to give us a call at our number listed below.

Good luck with your truck!